In a large bowl, lightly beat 2 eggs and add 1/2 tsp. salt and 1/4 cup water. Slowly add the flour and mix gently, kneading as you go. Dough should be smooth, but not too dry. Add a little water if needed. Let rest in bowl, uncovered, for 30 minutes. While the dough is resting prepare the filling.

If using cooked brisket, just fill the dough with 1 tbsp. of brisket. Fold over the shape and press the edges down. If using uncooked brisket or uncooked ground beef, do the following: Heat chicken fat (or oil) in a large skillet and add the onions, 1/2 tsp. salt, and pepper. In a medium bowl, mix the beef with the egg and add to the skillet. Cook until meat is fully cooked. Let the meat mixture cool before filling the dough.

On a floured board, roll out the dough. Cut into 3 inch squares or circles, using a drinking glass or biscuit cutter, or cut into triangles. Fill each shape with 1 tbsp. of the meat mixture and cover each by pulling the dough over the filling and pressing down on the edges.

After filling the dough, let the kreplach dry on a plate or paper towels for about 1 hour. Boil water and add a little salt. Add the kreplach and cook for 15 to 20 minutes.

Heat 1/4 to 1/2 cup vegetable oil in a large skillet on medium heat. Fry kreplach for 3 minutes per side until golden brown. Watch to make sure they don't burn. Let kreplach drain on paper towels to absorb excess oil.

In a small bowl, mix apricot preserves with 1-2 tsp. of Dijon mustard. Mix well. Taste and add more or less mustard to your liking (you are looking for a sweet/sour balance). Serve with fried kreplach.